US Airways Express Flight 4561
Beech 1900D · Incident: propeller failure/malfunction during initial climb
From Syracuse Hancock International Airport (SYR) to Boston Logan International Airport (BOS)
Event
- NTSB case
- NYC98IA106
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Incident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Airline
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Beech 1900D
- Aircraft type
- Beechcraft 1900
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N832CA
- Operator
- US Airways Express
- Onboard fatalities
- Unknown
- Route
- From Syracuse Hancock International Airport (SYR)To Boston Logan International Airport (BOS), Boston, MA
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 121: Air Carrier
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Initial climb
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Propeller failure/malfunction
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Minor
Cause areas
- Other maintenance personnel › Maintenance, improper
- Other maintenance personnel › Maintenance, inspection, inadequate
- Propeller system/accessories, counterweight › Cross/stripped threaded
Approximate · Estimated position: the centre of Syracuse, NY, the place the record names. Not the accident site.
NTSB narrative
After takeoff, the pilot heard a 'loud bang' followed by severe vibration. The pilot returned and landed at the departure airport without further incident. Examination revealed the left engine's number two propeller counterweight had separated, and exited through the propeller spinner. The counterweight then impacted the number one propeller blade, of the left engine, which separated about 12 inches from the hub. Examination of the counterweight clamp leading edge bolt hole revealed that the internal threads in the hole were stripped by motion of the leading edge bolt out of the hole. Additionally, the hole contained a double set of thread roots, indicative of cross threading of a bolt or mistapping of the threads. The propeller counterweight bolts had been replaced during an overhaul performed by the propeller manufacturer on April 12, 1995. The propeller counterweight bolts were also replaced by a certified propeller repair station, during maintenance on April 8, 1996, and at the last overhaul, which was performed on January 28, 1997. According to the propeller overhaul manual, after removal of a counterweight clamp bolt, an undersized tap should be used to remove the loctite retaining compound which was to be applied to the counterweight clamp threads during installation. The manual also stated '...Visually inspect threads for damage. Cross threading, damaged or missing threads is cause for retirement of the clamp.' A representative from the propeller repair station stated that their mechanics use a compressed air plastic bead spray to clean the clamp threads and they do not use an undersized tap. According to the propeller manufacturer, the use of a compressed air plastic bead spray to clean the propeller counterweight clamp threads was not an approved procedure.
Probable cause
Improper maintenance which resulted in a cross threaded\ mistapped counterweight bolt hole, and the subsequent failure of the propeller counterweight clamp assembly. Also causal was the inadequate inspection of the counterweight clamp threads by maintenance personnel which failed to detect the damaged counterweight threads.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record NYC98IA106
- Event ID
- 20001211X10175
- Case number
- NYC98IA106
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (5)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 6a9e831c678b323403a29b9ab417020fb1af160833bdbe37714712dab9782fdd; retrieved 2026-09-18T17:09:59.949Z.
- The NTSB's operator name is blank for N832CA; the operator shown is the name the NTSB records it doing business as.